1. Field of the Invention
The present invention relates to a passenger detector for detecting whether a seat of an automobile is occupied by a passenger or not and for detecting a weight of the passenger occupying the seat. The present invention also relates to a method for adjusting such a detector after it is mounted on the seat.
2. Description of Related Art
Various types of the passenger detectors have been known hitherto. One is a detector that detects a passenger's weight imposed on the seat based on pressure changes detected by a pressure sensor installed under the seat. Another one is a detector that uses a pressure-sensitive sheet and a device for measuring a hip size of the passenger. Yet another one is a detector that uses a strain gage installed in the seat. It is necessary for any type of the passenger detectors to adjust or calibrate a zero-weight point or threshold values memorized in the detector for determining a weight of a passenger occupying the seat, because the detector is affected by distortion or strain caused in a process of mounting the detector on the seat.
To cope with the above problem, JP-A-2000-258232 proposes a detector for measuring a passenger's weight on a seat by mechanically absorbing the distortions caused in the process of mounting the detector on the seat. In this detector, a mechanism for absorbing the distortions has to be included in addition to a primary mechanism for measuring the passenger's weight. Therefore, the detector becomes large in size, and it is difficult to install the detector under the seat. In addition, it is difficult to completely absorb the distortions and errors by a solely mechanical manner. Accordingly, it is not easy to realize a high accuracy in the detector.